Javascript React Native:将组件导入App.js时出错

从组件导入默认类时出错 使用expo，我搜索此错误，但没有解决问题，组件返回对象

类型无效--需要字符串（对于内置组件）或类/函数（对于复合组件）

但得到：object

错误：

12:19:03: Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

Check your code at registerRootComponent.js:35.
    in ExpoRootComponent (at renderApplication.js:33)
    in RCTView (at View.js:60)
    in View (at AppContainer.js:102)
    in RCTView (at View.js:60)
    in View (at AppContainer.js:122)
    in AppContainer (at renderApplication.js:32)

App.js

import Login from './app/components/login';

import React, {Component} from 'react';
import {Text, View} from 'react-native';

export default class Login extends Component {
    constructor(props){
        super(props);
        this.state = {}
    }
    render(){
        return(
            <View>
             <Text>Login</Text>
            </View>
        )
    }
}

app/components/login/index.js

import Login from './app/components/login';

import React, {Component} from 'react';
import {Text, View} from 'react-native';

export default class Login extends Component {
    constructor(props){
        super(props);
        this.state = {}
    }
    render(){
        return(
            <View>
             <Text>Login</Text>
            </View>
        )
    }
}

import React，{Component}来自'React'；
从“react native”导入{Text，View}；
导出默认类登录扩展组件{
建造师（道具）{
超级（道具）；
this.state={}
}
render（）{
返回(
登录
)
}
}

在

App.js

中，对

登录

组件使用默认导入。另外，从

App.js

import React from "react";
import Login from './app/components/login';

export default class App extends React.Component {
  render() {
    return <Login/>;
  }
}

从“React”导入React；
从“./app/components/Login”导入登录名；
导出默认类App扩展React.Component{
render（）{
返回；
}
}

没什么，只有一行输入。